1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge including an electrophotographic photosensitive member, and an electrophotographic apparatus.
2. Description of the Related Art
As an electrophotographic photosensitive member to be installed in an electrophotographic apparatus, electrophotographic photosensitive members containing an organic photoconductive substance (charge-generating substance) have been used and widely studied.
In recent years, with increased use of charge-generating substances having higher sensitivity, there has been a problem in that decreases in sensitivity in charge-generating substances due to degradation by oxidation of charge-generating substances and changes in environment are observed. As a technique for improving a decrease in sensitivity of charge-generating substances, there are known techniques in which an anthraquinone derivative is incorporated into a charge-generating layer.
Japanese Patent Laid-Open No. 61-77054 (Patent Literature 1) discloses a technique in which an anthraquinone derivative is incorporated into a charge-generating layer in order to suppress degradation of a charge-generating substance due to ozone. Japanese Patent Laid-Open No. 2-97956 (Patent Literature 2) discloses a technique in which an anthraquinone derivative is incorporated into a charge-generating layer in view of an increase in the sensitivity of a charge-generating substance and stability in sensitivity and charging potential. Japanese Patent Laid-Open No. 10-63022 (Patent Literature 3) discloses a technique in which an anthraquinone derivative is incorporated into a charge-generating layer in order to adjust sensitivity. Furthermore, Japanese Patent Laid-Open No. 2006-30699 (Patent Literature 4) discloses a technique in which an anthraquinone derivative having an amino group or a hydroxy group is incorporated into a charge-generating layer in order to suppress the residual potential due to repeated use of a photosensitive member.
However, in addition to the problem described above, as a result of studies by the present inventors, it has been found that, by increasing the sensitivity of a charge-generating substance, the charge generation amount is increased, charges are likely to be retained in a charge-generating layer, and ghosting is likely to occur, which is a problem. Specifically, in an output image, a phenomenon called positive ghosting in which the density is increased only in portions irradiated with light during previous rotation or a phenomenon called negative ghosting in which the density is decreased only in portions irradiated with light during previous rotation is likely to occur. Even when any of the anthraquinone derivatives described in Patent Literatures 1 to 4 is used, suppression of ghosting is not sufficient in the case of repeated use of an electrophotographic photosensitive member.